In human body security check systems such as those utilizing X-rays, a body inspection image formed due to transmission or scattering of the rays contains anatomical characteristics inside or outside the human body. The security check, on one hand, needs to recognize from the image hidden contrabands such as guns, knives, explosives, and pellets of drugs swallowed inside, and on the other hand, should avoid causing public's concerns about invasion of privacy so as not to incur challenges and criticisms from the public.
Generally, some details of the body can be obscured by adjusting brightness and contrast of the image, which enhances inorganic matters such as metal while protecting privacy of a person under inspection. However, this will also obscure organic matters such as explosives and drugs, which are in low contrast to human tissues, causing serious safety troubles. The conventional image processing technology is capable of blurring anatomic details of the body, for example, by means of edge enhancement and filtering with respect to the whole image. However, it causes difficulties in recognizing suspicious objects which are thin, small-sized and light-weighted, resulting in a reduced possibility of detecting the contrabands.
To improve both the capability of detecting the contrabands and the privacy, protection level, some scanning systems segment the body inspection image into a foreground portion and a background portion or into a high-scattering portion and a low-scattering portion, and apply different image processes on the different portions before combining them again. For example, in the foreground portion, body details may be smoothed and inorganic matters such as metal may be enhanced based on a result of database-based comparison; while in the background portion, edge detection and enhancement may be performed. This brings significant advantages over the conventional technology. However, existing artificial intelligence algorithms cannot achieve a reliable automatic detection of contrabands which are irregular in shape and low in contrast, such as pellets of drugs swallowed inside or explosives in form of pieces hidden at the abdomen part in a low-dose X-ray transmission image. If such contrabands are deemed being body details and thus are smoothed, the image effect actually degrades with respect to that before blurring. This virtually increases the uncertainty of such scanning systems in detecting the contrabands.
Therefore, there is a need for a method of processing a body inspection image and a body inspection apparatus, by which it is possible to achieve a compromise between the privacy protection and the contraband detection.